The present invention relates to a changeover valve, particularly but not exclusively to a changeover valve for a vacuum cleaner.
An upright vacuum cleaner generally has a cleaner head rotatably mounted on the lower end of a main body in which dust separation apparatus is housed. The dust separation apparatus can be in the form of a conventional bag filter or in the form of a cyclonic separator consisting of one or two cyclones as shown and described in, for example, EP 0 042 723. A handle for propelling the cleaner across the floor to be cleaned is arranged to extend upwardly from or behind the main body. A pair of supporting wheels are mounted on the lower end of the main body or on the cleaner head. The cleaner head extends in a forward direction. A dirty-air inlet is located at the forward end of the cleaner head and facing downwardly so that, in use, the dirty-air inlet faces towards the surface to be cleaned. Dirty air is drawn into the dust separation apparatus via the dirty-air inlet by means of a fan driven by a motor. When the dirt and dust entrained within the air has been separated from the airflow in the separating apparatus, clean air is expelled into the atmosphere.
Upright vacuum cleaners are commonly convertible into cylinder cleaners. In the cylinder mode, the dirty air is drawn into the cleaner by way of a wand or hose attached to the vacuum cleaner instead of by way of the dirty air inlet located in the cleaner head. This cylinder mode facilitates cleaning of areas which cannot be easily reached by the cleaner head, for example, underneath furniture, on stairs or above the floor. The handle which is used to propel the vacuum cleaner across the floor in the upright mode is in some cases convertible into a wand and hose arrangement for this purpose. In either mode, it is necessary for the dirty air inlet which is not being used to be blocked or disconnected from the dust separating apparatus so that air is drawn into the cleaner only by way of the inlet suitable for the current mode of use.
The selection of the appropriate dirty-air inlet is carried out automatically in some known prior art machines in response to the positioning of the body and/or handle of the cleaner with respect to the cleaner head during cleaning. When the handle of the vacuum cleaner is put into a vertical position, ie the machine is being used in the cylinder mode, the dirty-air inlet is provided by a hose and wand attached to the vacuum cleaner and the inlet located in the cleaner head must be inoperative. When the handle is inclined with respect to the vertical, ie the vacuum cleaner is being used in the upright mode, the dirty-air inlet in the cleaner head is to be used and the dirty-air inlet in the hose and wand becomes redundant and must be disconnected from the dust separation apparatus. The changeover between the dirty-air inlets has previously been effected by sliding or rotating valves. An example of a rotating changeover valve is disclosed in EP 0 134 654 B. A disadvantage of the known valves used for this purpose is that, in order to effect the changeover, two abutting surfaces are made to slide across one another. This causes wear on the valve surfaces and particularly on the seals which surround the openings of the air passages. If the seals wear, the air passages cease to be airtight and losses can then occur which reduces the efficiency of the machine, particularly if it includes cyclonic separating apparatus. Wear can also occur at the pivoting supports of the movable part of the valve which can result in misalignment of the air passages and an increase in losses. Sliding changeover valves, in which the valve slides between its different positions, are also known but such valves also have the disadvantage that the valve surfaces, and in particular the surfaces of the valve seals, become worn down through the sliding contact over time. A further disadvantage of known changeover valves is that, if the seals do wear through use, the valve is difficult to access and replacing the valve or the seals of the valve is awkward and time consuming. A still further disadvantage of some known arrangements is that, immediately downstream of the valve, the airflow path includes a chamber having an enlarged cross-section in which the airflow expands and decelerates. This deceleration can lead to an accumulation of debris in or near the valve and this can lead to the valve becoming jammed or clogged. Expansion of the airflow path can also lead to power losses.
An object of the present invention is to provide a changeover valve in which the valve surfaces are less prone to wear during the changeover motion than in current changeover valves. A further object is to provide a changeover valve which is simple and cheap to manufacture but which is effective in use. A further object is to provide a changeover valve which can be easily and quickly accessed for maintenance, should any such maintenance be required. A still further object is to provide a valve in which the cross-sectional area of the airflow path is maintained constant or near-constant.
The provision of ramp and follower means on the valve members to move the valve members away from one another during changeover movement means that the valve members are out of contact with one another during the major part of the changeover movement. This reduces the wear suffered by the components and particularly by the seals located on the components. Reducing the wear on the seals prolongs the useful life of the changeover valve and improves performance during that time. Furthermore, the arrangement allows a positive sealing force to be applied when the valve is operational and this improves the seal achieved by the valve.
In a preferred embodiment of the invention, the changeover valve is incorporated in a vacuum cleaner. The first aperture of the second valve member communicates with the hose and wand and the second aperture communicates with the air inlet in the cleaner head. When the main body of the cleaner is in an upright position and the cleaner is in cylinder mode, the first valve member is automatically aligned with and sealed across the first aperture to allow the passage of air from the hose and wand to the dust separation apparatus. The dirty-air inlet in the cleaner head is automatically shut off. When the main body of the vacuum cleaner is inclined away from the vertical to put the cleaner into the upright mode, the movement of the main body relative to the cleaner head causes the first valve member to lift away from the first aperture of the second valve member so that the first valve member is no longer sealed against the first aperture of the second valve member. The first valve member is then moved to the second aperture of the second valve member whilst it is out of contact with the second valve member. It is then aligned with and sealed across the second aperture of the second valve member. In this position, air is allowed to flow from the cleaner head to the dust separating apparatus and the dirty-air inlet of the hose and wand is automatically shut off.
In a further preferred embodiment of the invention, one of the valve members has a portion on its surface which is located adjacent the periphery of the aperture or apertures and is shaped so that it acts as a ramp. The follower is formed by a protrusion on a surface of the other valve member. This protrusion is also located adjacent the periphery of the aperture or apertures. The protrusion may be in the form of a tongue or a nodule.
A further embodiment of the invention provides locking means to ensure that the first valve member is secured in position when aligned, with the second aperture even when the main body is inclined at different angles. Use of the vacuum cleaner in the upright mode involves frequent changes in the angle of inclination of the main body of the vacuum cleaner with respect to the vertical. It is important that the first valve member remains aligned with and sealed across the second aperture of the second valve member throughout this movement so that the air passage between the inlet and the dust separation apparatus is maintained.
The locking means preferably comprises a first catch on the first valve member which co-operates with a corresponding second catch on the main body of the cleaner. The second catch is pivotable and biased into a locking position so that the first valve member is held in alignment with the second aperture irrespective of the angle of inclination of the handle. The locking means is released by the action of a release member when the main body of the vacuum cleaner is returned to the upright position. The release member may be attached directly to, or form part of, the cleaner head casing.